dm table: don't copy from a NULL pointer in realloc_argv()
For the first call to realloc_argv() in dm_split_args(), old_argv is NULL and size is zero. Then memcpy is called, with the NULL old_argv as the source argument and a zero size argument. AFAIK, this is undefined behavior and generates the following warning when compiled with UBSAN on ppc64le: In file included from ./arch/powerpc/include/asm/paca.h:19, from ./arch/powerpc/include/asm/current.h:16, from ./include/linux/sched.h:12, from ./include/linux/kthread.h:6, from drivers/md/dm-core.h:12, from drivers/md/dm-table.c:8: In function 'memcpy', inlined from 'realloc_argv' at drivers/md/dm-table.c:565:3, inlined from 'dm_split_args' at drivers/md/dm-table.c:588:9: ./include/linux/string.h:345:9: error: argument 2 null where non-null expected [-Werror=nonnull] return __builtin_memcpy(p, q, size); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~ drivers/md/dm-table.c: In function 'dm_split_args': ./include/linux/string.h:345:9: note: in a call to built-in function '__builtin_memcpy' Signed-off-by: Jerome Marchand <jmarchan@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
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@ -561,7 +561,7 @@ static char **realloc_argv(unsigned *size, char **old_argv)
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gfp = GFP_NOIO;
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}
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argv = kmalloc_array(new_size, sizeof(*argv), gfp);
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if (argv) {
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if (argv && old_argv) {
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memcpy(argv, old_argv, *size * sizeof(*argv));
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*size = new_size;
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}
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